The present invention relates to a stable, low viscosity bimodal oil in water emulsion and, more particularly, a bimodal oil in water emulsion having a discontinuous oil phase characterized by two distinct mean diameter oil droplet sizes. The present invention further relates to a method for producing a stable, low viscosity bimodal oil in water emulsion whose viscosity does not age over time.
Reserves of viscous hydrocarbons are plentiful. Low API gravity, viscous hydrocarbons found in Venezuela, Canada, the Soviet Union and the United States have viscosities ranging from 10,000 to more than 500,000 centipoise at ambient temperatures and API gravities of less than 15. These oil reserves are generally located at remote places far away from the large oil consumption centers of the world.
Viscous hydrocarbons of the type aforesaid are currently produced either by steam injection in combination with mechanical pumping, mechanical pumping itself, or by mining techniques. Because of the high viscosity of the viscous hydrocarbons it is impossible to handle them by conventional equipment. The alternative methods developed for handling viscous hydrocarbons tend to be very expensive.
The formation of emulsions of viscous hydrocarbons in water allows for improved handling of the viscous hydrocarbons as, under certain conditions, the viscous oil in water emulsions have lower viscosities than the viscous hydrocarbons themselves. It is well known in the art to transport viscous hydrocarbons by first forming a viscous hydrocarbon in water emulsion and thereafter pumping the emulsion which is at a lower viscosity through conventional pipelines. Generally, the viscous hydrocarbon in water emulsions formed for transportation in the manner described above comprise emulsions where the dispersed phase content of viscous oil in the oil in water emulsion is less than or equal to 70% by weight. The oil content is classically limited to a maximum value of 70% by weight as a result of the fact that emulsion viscosity increases in an exponential factor when the dispersed oil phase increases beyond 70% by weight. In addition, for viscous hydrocarbon in water emulsions having dispersed oil phase concentrations of greater than 70% by weight and monomodal mean diameter droplet size distribution, conventional means for transporting the emulsions become inoperative due to the high viscosity of the emulsions and the complexity of the realogical behavior of the emulsions as a result of the visco-elastic nature of these emulsions. It is well known in the prior art that the realogy properties of oil in water emulsions are significantly influenced by distribution and the mean diameter oil droplet size. Thus, for any known viscous hydrocarbon in water ratio in an oil in water emulsion and for any given mean diameter oil droplet size distribution, the viscosity of the resultant oil in water emulsion diminishes when the oil droplet size distribution becomes more poly-dispersed. In other words, a mono-dispersed emulsion has a viscosity greater than the same emulsion with a poly-dispersed droplet size distribution.
It is highly desirable when transporting these high dispersed phase concentrated viscous hydrocarbon in water emulsions by pipeline or tanker over large distances to increase the internally dispersed viscous hydrocarbon phase to a maximum possible value. By maximizing the viscous hydrocarbon content of the emulsion the cost for transportation is decreased per unit of viscous hydrocarbon. Furthermore, when these viscous hydrocarbon in water emulsions are used directly as fuels in power plants, the greater viscous hydrocarbon concentration in the emulsion results in a corresponding greater energy output by unit volume of the emulsion.
Accordingly, it is the principal object of the present invention to provide a viscous hydrocarbon in water emulsion characterized by a high internal phase concentration of viscous hydrocarbon, a relatively low viscosity and stable viscosity over time.
It is a further objection of the present invention to provide a viscous hydrocarbon in water emulsion as aforesaid which is characterized by a distinct bimodal dispersed viscous hydrocarbon oil phase.
It is a still further object of the present invention to provide a viscous hydrocarbon in water emulsion as aforesaid wherein the viscosity of the emulsion can be readily adjusted and modified without further shearing of the emulsion product.
It is a further principal object of the present invention to provide a method for preparing a stable, low viscosity bimodal viscous hydrocarbon in water emulsion which is resistant to aging over time and may have viscosity modifications made to any desired value for fulfillment of any end use requirement.